ANN ARBOR—Children as young as 3 years old understand they should share with others, but they fail to follow this rule until age 7 or 8, according to a new University of Michigan study.

"There is abundant evidence that children are aware of fairness standards at a young age, yet young children often allocate resources unfairly when they stand to benefit," said Craig Smith, a U-M postdoctoral psychology researcher and the study's lead author.

Smith and colleagues Peter Blake of Boston University and Paul Harris of Harvard University wanted to learn more about the gap between children's judgment and their behavior. The study also shed light on the youngsters' will power when faced with the actual decision of sharing.

The study involved 102 children, whose ages ranged from 3-8. Each received four stickers. With their parents nearby, the children were asked how many stickers they should share with another child. Overall, they thought sharing was the right thing to do in this situation in which both parties were equally deserving, the researchers said.

"Irrespective of age, children judged that a norm of equal sharing applied to both themselves and others," Smith said.

However, this is where the similarities between the age groups ended. When the moment occurred to share, younger children hoarded their stickers by offering less than an equal split. By 7-8 years of age, children equally shared their treasure.

Perhaps young children fail to share equally because they expect others to hoard, although this doesn't seem to be the case, the researchers said.

"In fact, they expected other children to share at least half of the stickers in the same situation," Smith said.

The researchers also noted that younger children may have limited self-control regarding fairness when faced with a conflict between sharing and their impulse to take for themselves. However, when asked, surprisingly these younger children correctly predicted that they would share less than half.

"They did not suffer from a last-minute failure of will power when faced with an actual decision," Smith said. "Instead, the youngest kids were aware that they would share less than the norm when they were asked to predict how many stickers they would share."

One thing the researchers did find was that, in the moment of sharing, the older children seemed to place more weight on the norm of equal sharing.

"The oldest kids stayed focused on thoughts about fairness and kindness," Smith said. "But when the younger kids had a chance to share, they often became focused on their desire to have all of the stickers for themselves."

Still, this study and others like it find that most children do become more generous with age, so parents and teachers have no reason to fret.